Mechanical aerator



June 11, 1940. E. B. MALLORY MECHANICAL AERA'I'OR Filed May 18, 1938 3Shoets-Shee t 2 l VENTOR 'z'oamJ 6?, 1.46 BY I k d ATToRfiEzs June 11,1940. E. B. MALLQRY NECHANICAL ABRATOR Filed lay 1a. 1938 3 Shouts-Sheet5 INVENTOR Patented June 11, 1940 UNITEDI STATES PATENT OFFlCE amonmoar..mmvroa Edward B. Mallory, Tenafly, N. 1.

Application my 1a, 1938, Serial No. 208,521

4 Claims. (01. 259-95) The invention relates to aerators as used in thepurification of sewage and analogous waste liquors, for the purpose ofoxidizing unstable putrescible components of the sewage to convert them5 into more stable forms, as well as to Intermix the liquid componentsof the sewage with the solids suspended therein. In waste purificationby the activated or oxidized sludge process for example, incoming sewage(after appropriate so-called primary treatment) is fed into the aeratorinadmixture with sludge particles recirculated back into the system froma previously completed cycle, and the aerator serves to oxygenate themixed I liquor thus constituted and to bring the recirculated sludgeparticles into contact with'the liquid and solid components of theincoming sewage, thereby accelerating the rate of chemical reactions.

The invention also relates particularly to aerators of the type whereinthe contents of the aerator are mechanically moved to expose them to theoxygenating action of the surroundingair and to intermix their solid andliquid components, in

contrast with aerators of the so-called diffusion type wherein air isbubbled up through the contents of the aerator. Heretofore mechanicalaerators of the so-called draft tube type have been of decidedly limitedcapacity in respect to the volume of waste liquor which could be therebyadequately treated, and one important object of the invention is toprovide a mechanical aerator of the last mentioned type which willenable markedly augmented capacity to be obtained in the above respects.I

present invention aims to provide such an aerator wherein circulation ofthe liquor in all portions of the liquor column within the aeratingchamber will be positively and directly brought about. thereby to insurecompleteness and uniformity of w treatment throughout the chamber andavoid dead spots in which a reduced rate of the desired chemicalreactions might otherwise occur or in which solids might otherwisereside for undesirable periods and become septic. thereby in- 5 creasingthe residual load on the process. The

invention has special advantages under conditions of operation whereinit is desired to aerate a heavy mixed liquor, i. e. one containing ahigh sludge content. Further objects and advantages o of the inventionwill be in part obvious and in part specifically referred to in thedescription hereinafter contained which, taken in conjunc- 'tion withthe accompanying drawings, discloses certain preferred forms ofapparatus operable in ;5 accordance with the invention; such apparatusFrom another aspect, the

of Fig. 1 looking in the direction of the arrows. 10 r I Fig. 4 is acentral vertical section of another form of apparatus constructed tooperate in accordance with the invention.

Fig. 5 is a plan view of the apparatus shown in Fig. 4.

Fig. 6 is a detail section taken on line 6-8 of Fig. 5 looking in thedirection of the arrows.

Fig. 7 is a view similar to Fig. 6 but showing a somewhat modifiedconstruction.

In-Flgs. 1 to 3 I have illustrated a simple form '20 1 of aeratingapparatus constructed to operate in accordance with the invention andincluding a chamber I having a suitable floor 2 and an enclosing sidewall 3 which preferably is substan* tially circular in cross section.Sewage mixed 25 liquor to be treated may be fed into chamber I through asuitable feed conduit 4 and withdrawn from the chamber through anoiitake conduit I which in the present instance. is in communicationwith the bottom portion of chamber I 30 through a vertical passageway!adjacent the enclosing side wall I of the chamber.

In accordance with the present invention I provide in the chamber I anupstanding draft conduit I through which mixed liquor in the cham- 35her is caused to circulate, and I employ in connection with such draftconduit. mixed liquor conducting members opening into the bottom portionof chamber I, at points so spaced about or distributed over the bottomof the chamber, that 40 all portions of the liquor column in the chamberwill be served substantially equally and uniformly by the'draft conduitand mixed liquor conducting members. The form of the invention shown inFigs. 1 to 3 may be readily arranged either to cause mixed liquor to bedrawn into the mixed liquor conducting members from the bottom portionof chamber I and circulated upwardly through the draft conduit I anddischarged into the upper portion of the chamber, or the mode ofoperation may be such that mixed liquor is drawn from an upper level ofchamber I into draft conduit I and circulated downwardly through thedraft conduit and mixed liquor conducting members to be delivered atpoints distributed over the bottom portion of the chamber. Preferablythe mixed liquor conducting members are moved relative to the mixedliquor contained in the bottom portion of'the aerating chamber tofurther augment the uniformity and completeness of treatment. In theform of the invention shown in Figs. 1 to 3 the draft conduit l islocated substantially in the central vertical axis of chamber I and themixed liquor conducting members above mentioned take the form ofradially extending hollow header members or pipes 8 disposed in thebottom portion of the chamber and communicating with draft conduit 1 attheir inner ends. These header members 8 are provided with openings 9spaced across the bottom portion of the chamber, the openings 9 beingprovided in the present instance in hollow nozzle-like members l0extending from the headers 8 as shownmore in detail in Fig. 3. Headers 8may be braced in position by suitable tie-rods ii.

In the upper portion of draft conduit 1 I provide a liquid pumpindicated generally at i2 in Fig. 1, and which will not be described indetail since suitable forms thereof are known in the art. As shown, thispump is driven by a motor i3 supported on a fixed superstructure l5overlying the aerating chamber, the motor being connected to the pump byshaft l6. If the pump l2 be assumbed to be arranged to draw mixed liquorupwardly through draft conduit I, the distribution of the openings 9over the bottom portion of the chamber, will cause the mixed liquor tobe drawn into headers 8 from numerous points distributed around thebottom of the chamber, from whence the mixed liquor will pass upwardlythrough draft conduit 1 and pump.

i2, from whence itv will be suitably distributed over the upper portionof the chamber. As shown in Figs. 1 and 2 the pump l2 delivers into aplurality of radially extending weirs or troughs II which overlie themain'body of liquid contained within the chamber and cause thecirculated mixed liquor to be distributed fairly uniformly over variousareas of the tank. These weirs Il may have suitable braces l8 to :assistin holding them in position on draft conduit 1, and tie-rods i9 (Fig. 2)may be used between the several weirs. Similar tie-rods 20 may be usedextending between the outer portions of the headers 8. v

Preferably the liquid conducting members or headers 8 above described,and their openings 9, are moved relative to the mixed liquor in thebottom portion of chamber i so as to serve different zones of the mixedliquor successively and enable substantially uniform treatment to beobtained with a smaller number of liquid conducting members. In the formof the invention shown in Fig. 1 the draft conduit 1 and parts carriedthereby, are suspended from the superstructure I5 by a 'collar 2| whichr'otatably surrounds shaft l8 but is fixed with respect 'to draftconduit 1 and associated parts, in such manner that when draft conduit 1is moved angularly substantially about the central axis I of chamber i,the liquid conducting members In the form of the invention underdiscussion the draft conduit and mixed liquor conducting members areslowly rotated by a gear 22attached to collar 2|, and driven in turn bya pinion 28 and reduction gearing 24 connected to a suitable motor 25,the last mentioned parts being supported by the fixed superstructure l5.

Whether the apparatus be arranged to draw in liquor from the bottom ofthe tank and discharge it over the top, or vice versa, the mixed liquorconducting members 8 and their openings 9 being distributed over thebottom portion of chamber i as above described, will positively anddirectly cause mixed liquor to be substantially uniformly withdrawn fromor conducted to the various areas of the bottom of the tank, overcomingthe tendency which the sludge particles otherwise would have to becomequiescent and settle out in local areas at the bottom of the chamber.The uniform and complete circulation obtained as above described ishighly important in intermixing all of the solid particles thoroughlywith the liquid components of the liquor, and in insuring adequateexposure of all portions of the mixed liquor to the oxygenating effectof the air into contact with which the mixed liquor passes during partof the circulation cycle. The apparatus also enables much heavier mixedliquors to be treated (that is containing higher sludge content) ascompared to prior circulating draft pipe arangements wherein the naturaldrift 'of the sludge particles was relied upon to keep them in thecirculating streams. with these prior arrangements only light mixedliquors could be treated, otherwise some of the sludge would settle outat local points and become septic, a difficulty which is avoided by theabove mentioned direct and positive circulation obtained atsubstantially all points over the bottom of the chamber. Acceleratedrates of purification and increased rates of decolorlzation of tradewastes for example may be obtained by employing mixed liquors of highsuspended solids concentration In prior aerators oi the so-called drafttube'type mixed liquors having suspended solids concentration higherthan about 2000 to 2500 p. p. m. could not be .used, whereas withapparatus constructed in accordance with the present invention mixedliquors having a suspended solids concentration from 4000 to 5000 p. p.m. may be employed where the sewage or waste characteristics make thishigh range of concentration desirable. When heavy concentrated mixedliquors are treated in an aerator oi the diffusion type, substantialquantities of the suspended solids adhere to the rough surfaces of theporous diil'users and slowly cause clogging and consequent increase inthe air pressure required to force proper amounts of air through thedifluser, thereby increasing operating costs and requiring cleaning ofthe dilfusers from time to time. Apparatus constructed in accordancewith the present invention is free from these difllculties.

In the past it has been the general practice in the art to employmechanical aerators of the draft tube type only in plants of relativelysmall capacity. This was necessarily so because of the greatmultiplicity of tanks which would be required for a larger installation,each individual aerator being limited in size because of the diflicultyof keeping all portions of the aerator contents adequately incirculation if a tank of large dimensions should be employed. Inaccordance with the present invention the direct and positivecirculation to different parts of the tank, also the movability of theliquid conducting members with'respect to the contents of thetank,,enable adequate and uniform treatment to be obtained with anaerator of much increased capacity.

. Figs. 4 to 7 show the invention as carried out by an apparatussomewhat diflerently constructed, wherein an aerating chamber It isdefined by an outer enclosing side wall 21 and an inner side wall N,which wallspreferably are substantially circular in'shape andsymmetrically disposed about a common central axis. Mixed liquor may befed into chamber 2' through an intake conduit II and withdrawn therefromthrough conduit it which in the present instance conducts theae'ratedmixed liquor into a clarifer or settling chamber 3| concentricwith aerating chamber 20. In the settling chamber 8| the solidswillsettle out to form a sludge blanket in the bottom of the settlingchamber, and sludge may be withdrawn through a discharge passageway Iileading through the bottom wall 32 of the clarifler, for recirculationinto the aerating chamber along with incoming sewage, and for disposal.Clarified eiiiuent may flow out from clariiier chamber 3| over anannular weir 33 and down through a duct 14 adjacent wall It to dischargeconduit 35 passing under the floor 36 of aerating chamber 26 to thereceiving waters of the region.

In the form of the invention shown in Figs. 4 and a plurality of draftconduits 81 having pumps 38 with driving motors It, mixed liquorconducting members 40 with openings ll (generally similar respectivelyto the members I, l2, l3, 8 and 9' previously described in connectionwith Figs. 1 and 2) are provided, and are mounted so as to be angularlymovable about the central axis of the annular aerating chamber 26. Forsupporting and moving the draft conduits 31, a rotary supportingstructure overlying the chambers 26 and 8! may be used, this structurebeing shown as having I-beams 42 assembled into the fan-shaped formshown. in Fig. 5 and journaled on trucks l6 and 4! provided with wheelsrunning on rails 48 and 40 carried respectively by the side walls 28 and21. As

shown in Fig. 4 the supporting structure may also'have a central supportand bearing 5. carried by a supporting pillar 5| located at the centralaxis of the apparatus. In the construction shown more in detail in Fig.6, the pumps 38 deliver into mixed liquor distributing members 52 shownin the form of pipes suitably suspended from the overlying supportingstructure and provided with nozzles 53 through which the mixed liquor issprayed onto the upper portion of aerating chamber 25.

In the form of the invention now under discussion the pumps 38 drawmixed liquor fromthe bottom portion of chamber through the openings Mrespectively associated therewith. and the mixed liquorconductingmembers 40 extend substantially all the way across chamber 26so that as the overhead supporting structure is rotated (which may bedone by a suitable motor and gearing as indicated generally at 54)v,tlie -several sets of openings 4! are carried pro- Thus theuniformity. and completeness of- 'treahment is augmented by moving thedraft conduits I1 themselves bodily. in addition to the mixed liquordistributing members 82, with rescribed, the rate of aeration may begoverned in accordance with the load on the plant (measured in terms ofB. 0. D. concentration) by suitably varying the rate of flow through thedraft conduits, for example by the use of variablespeed driving motorsor by suitable valve arrangements used in conjunction with the pumps, orby slowing down or entirely stopping some of the pumps. In previousaeration plants involving draft tubes, the capacity of the aeratorsbeing necessarily limited as above described, a number of tanks inseries were necessary to accommodate sizable-loads, and should one ofthe motors or pumps become. disabled for any reason, the entire volumeof liquid in the corresponding tank would no longer receive treatment,and unless the condition were promptly corrected thesludge would settleout of the mixed liquor in that particular tank and become septic, thusgreatly adding to the load on the plant and decreasing purificationobtained. In the form of apparatus last above described this objectionis obviated since if one of the pumps should go out of service theremaining units will still be moved progressively to'treat the entirebody of liquid in the tank, preventing the sludge from settling out orbecoming septic. As shown the beams 42 also carry uprights 56 located inthe clarifler 3i, and carrying sludge collecting members denotedgenerally at 51 which assist in removing sludge from the blanket whichis formed in the bottom of the clariiier chamber. These members 51should be regarded as merely typical of mechanism for assisting in theremoval of the sludge, several forms of which mechanism are known in theart. In most instances the efficiency of the sludge collecting membersis increased by moving them angularly as above described.

Fig. '1 shows a somewhat modified construction wherein troughs 58 areemployed as substitutes for the distributor pipes 52 to-receive themixed liquor drawn up through draft conduits l1 and discharged by pumpsll, these troughs 58 being shown in Fig. 7 as being provided with holes58 through which the mixed liquor may pass to the upper portion ofchamber 26'. These troughs I may be likewise supported by and movablewith the overhead supporting structure above referred to. The rate ofoxygenation of the liquids in the aerating chamber is accelerated byagitating the surface of the liquid in the tank, or by spraying orallowing to fall through the air in relatively small masses, the mixedliquor drawn up from the bottom of the tank in the case of the upwardflow draft conduits above described. Similar devices for agitating andexposing the contents of the aerating chamber to the air, areadvantageous in installations in which the mixed liquor flows downwardlythrough the draft conduit or conduits.

' While the invention has been disclosed as carried out by apparatus ofcertain particular con- 3 ly over different parts of theaeratingchamberdisposed invsaid chamber, means for circulating mixedliquor through said conduit, mixed liquor conducting memberscommunicating with said draft conduit and having openings communicatingwith the bottom portion of said chamber at points spaced between saidwalls, means for moving said draft conduit and liquid conducting membersangularly substantially about said central axis to cause the aforesaidopenings of said liquid conducting members to travel through the bottomportion of said chamber, and means affording passage of mixed liquorbetween the upper portion of said draft conduit and the upper portion ofsaid chamber.

2. A mechanical aerator of the class described including a chamberhaving outer and inner walls disposed substantially symmetrically about"a central axis, means for feeding mixed liquor into said chamber andfor withdrawing mixed liquor therefrom, a supporting structure overlyingsaid chamber, an upwardly extending draft conduit disposed in saidchamber, means for circulating mixed liquor through said conduit, saiddraft conduit and said last mentioned means being carried by saidsupporting structure, means for moving said supporting structureangularly substantially about said central axis thereby to cause saiddraft conduit to travel about in said chamber, and mixed liquorconducting members communicatlng with said draft conduit and havingopenings communicating with the bottom portion of said chamber at pointsspaced between said walls, said mixed liquor conducting members beingalso supported from and movable with said supporting structure.

3. A mechanical aerator of the class described including a chamber,means for feeding mixed liquor into said chamber and for withdrawingmixed liquor therefrom, an upwardly extending draft conduit disposed insaid chamber, means for causing mixed liquor to circulate through saiddraft conduit, mixed liquor conducting members having passagewayscommunicating with said draft conduit and opening into the bottomportion of said chamber at points spaced across the latter, means formoving said draft conduit and said mixed liquor conducting members aboutwithin the bottom portion of said chamber, and means affording passageof mixed liquor between the upper portion of said draft conduit and theupper portion of said chamber.

4. A mechanical aerator of the class described including a chamber,means for feeding mixed liquor to said chamber and for withdrawing mixedliquortherefrom, a supporting structure rotatable about an axis which issubstantially centrally disposed with respect to said chamber, anupwardly extending draft tube disposed in said chamber and spaced fromsaid axis of rotation, said draft tube having means therein for causingmixed liquor to circulate therethrough, a mixed liquor conducting membercommunicating with said draft tube and having openings communicatingwith the bottom portion of said chamber at points variously spaced fromsaid axis of rotation, said draft conduit and mixed liquor conductingmember being attached to and rotatable with said supporting structure.

EDWARD B. MALLORY.

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